typed_result 2.0.0

A result monad with two subtypes representing a success or a failure

typed_result provide a convenience Result monad to represent success and error.

A Result<T, E> class can be either a success (Ok<T> class) or an error (Err<E> class).

// Result<T, E>  --+-- Ok<T>
//                 |
//                 +-- Err<E>

Features

This package aims to provide convenience methods for:

• Getting a value (get, getOr, getOrThrow, getError, getErrorOr and getErrorOrThrow)
• Mapping a Result value into another Result (map, mapError and mapBoth)
• Execute a block based on the result (onSuccess and onFailure), (when)
• Wrap a block, transforming it's exception into error (runCatching)
• Wrap any value to a result based on the nullability (toResultOr)
• Testing results with custom matchers

Usage

An Result<T, E> can't be instantiated directly. To create a Result, simply create an instance of Ok<T> or Err<E>.

var result = Ok(1); // as Ok<int>
var result = Err(""); // as Err<String>
Result<int, String> result = Ok(1); // as Result<int, *>, where * can be defined with any type
Result<int, String> result = Err(""); // as Result<*, String>, where * can be defined with any type

// As a return of a function
Result<int, String> getData() {
  if(condition) {
    return Ok(1);
  } else {
    return Err("");
  }
}

Additional information

This package is hugely based on a Kotlin library made by Michael Bull.

The motivation for creating this package comes from using this library in Kotlin projects and missing these features in Dart.